Abstract: Azure B is a Phenothiazine class of dye in which an atom of sulphur replacing oxygen in heterocyclic ring. They have color range from green to blue and have been used for coloring paper, tannin mordant cotton, silk and leather. The decoloration and mineralization of the Azure B dye under condition of visible light and TiO₂ photocatalyst was studied. The textile waste-water from dyeing process normally contains considerable amount of chloride and carbonate ions. These chemicals are often used in textile processing operations for adjusting the P^H of the dye bath It is a important to study the effect of chloride and carbonates on the treatment efficiency. This study confirms that the presence of Na Cl and Na₂CO₃ led to inhibition of the degradation process.